1. Field of the Invention
The present invention relates to circuit designs, and more particularly, to power distribution network designs of integrated circuit designs.
2. Description of the Prior Art
In an integrated circuit design, a power/ground (P/G) network which distributes power voltages and/or ground voltages from power source locations to each circuit block (e.g., macro or cell) of an integrated circuit system is essential. No matter the type of integrated circuit system (e.g., a chip, such as a wire-bond chip or a flip chip), each circuit block that provides at least a function has to be connected to a power source (e.g., VDD) and a ground source (e.g., VSS) to be functional.
For modern circuit designs, the architectures of the P/G networks face grave challenges. Due to the fast switching frequencies and increasing power consumption of the latest integrated circuit systems, large switching currents intermittently occur at the power and ground networks, thereby degrading the performance and reliability of the integrated circuit system. Moreover, the resistance of the power traces constituting the P/G network leads to a voltage drop (i.e., IR drop) over the power source nodes to the center of the P/G network. Sometimes the excessive voltage drop across the power network, or the ground bounce across the ground network, will reduce the switching speeds of the circuit system and shrink the noise margins of the integrated circuit system, which may lead to functional failures. In addition, the large current across the P/G network may cause the power traces in the metal wires to be worn out as a result of electronic migration (EM). The electronic migration diminishes the reliability of the integrated circuit systems; in a worst case, it may result in eventual losses of one or more connections of the P/G network, thereby leading to intermittent failure of the whole integrated circuit system.
It is therefore an objective in the field to design a robust power network and/or ground network that uses a smaller area of metal wires while still assuring reliability of the functionality of an integrated circuit system.